1. Field of the Invention
The present invention relates to a suction adherence conveying device for printing plates in which a printing plate or an interleaf sheet accommodated in a magazine is suction-adhered by suction cups and taken out one sheet at a time from the magazine in that state.
2. Description of the Related Art
A technique (an automatic exposure device for printing plates) has been developed in which a printing plate (which will be referred to as a photopolymer plate, hereinafter) in which a photosensitive layer (for example, a photopolymerization layer) is provided on a support is used and an image is directly recorded on the photopolymerization layer of the photopolymer plate by a laser beam or the like.
In the technique described above, recording of images onto photopolymer plates is performed rapidly, and thus, it is required to feed photopolymer plates continuously. As a result, a plurality of photopolymer plates and interleaf sheets for protecting the plate surfaces of the photopolymer plates are accommodated in a magazine in a state in which they are stacked alternately, and stand-by in this state at a predetermined position, and are suction adhered by a suction section comprised of suction cups and a fan. The plurality of photopolymer plates and interleaf sheets are thereby automatically taken out one sheet at a time, and only the photopolymer plates are fed to an exposure section.
Accordingly, when a photopolymer plate or an interleaf sheet accommodated in the magazine in the stacked state are taken out, they are differentiated on the basis of predetermined differentiation signals. Based on the results of determination as to whether a photopolymer plate or an interleaf sheet has been removed, a portion of a conveying path is switched such that only the photopolymer plates are conveyed to the exposure section, and the interleaf sheets are conveyed to an interleaf sheet stacking device.
In the above-described conventional suction adherence conveying device for printing plates, for example, the photopolymer plates and the interleaf sheet are differentiated by a difference in reflectances of the photopolymer plates and the interleaf sheets by using a photoswitch.
However, photoswitches are expensive, and there is the concern that photopolymer plates which have not yet been exposed may be sensitized by light of the photoswitch.
In view of the aforementioned, an object of the present invention is to provide a suction adherence conveying device for printing plates which is low-cost and can distinguish between printing plates and interleaf sheets taken out from a magazine without sensitizing the unexposed printing plates.
A first aspect of the present invention is a suction adherence conveying device for printing plates comprising: suction cups which are provided so as to be able to approach and move away from a surface of a printing plate or an interleaf sheet accommodated in a magazine; a suction section which is communicated with the suction cups through communicating paths and sucks in air from the suction cups, and due to the suction section sucking in air from the suction cups, the printing plate or the interleaf sheet is vacuum-suction-adhered and removed from the magazine in this state one at a time; and a pressure sensor which is set in communication with the communication paths, and detects that a degree of vacuum at the time of suction-adhesion by the suction cups is greater than or equal to a first degree of vacuum set to correspond to a case in which the interleaf sheet is suction-adhered, and detects that the degree of vacuum at the time of suction-adhesion by the suction cups is greater than or equal to a second degree of vacuum which is set to correspond to a case in which the printing plate is suction-adhered and which is higher than the first degree of vacuum.
Here, the first and second predetermined degrees of vacuum are set based on the capacity of the suction section and the air permeability between the suction cups and the material to be suction-absorbed (the printing plate or the interleaf sheet).
Further, the pressure sensor of the suction adherence conveying device of the first aspect of the present invention may be a pressure sensor which outputs signals which are linear with respect to the degree of vacuum. Or, the pressure sensor may be two or more pressure switches which each output a predetermined signal (such as a signal turning a contact ON/OFF) when the degree of vacuum is greater than or equal to a predetermined degrees of vacuum. Alternatively, the pressure sensor may be a single pressure switch which has two or more set vacuum degrees and outputs different signals (such as a signal turning a contact ON/OFF and combinations thereof when the degree of vacuum is greater than or equal to the set degrees of vacuum.
In the suction adherence conveying device for printing plates of the first aspect of the present invention, in a case in which the suction cups suction-adhere an interleaf sheet, the pressure sensor detects the fact that the degree of vacuum at the time of suction adherence by the suction cups is greater than or equal to the first predetermined degree of vacuum. On the other hand, in a case in which the suction cups suction-adhere a printing plate, the pressure sensor detects the fact that the degree of vacuum at the time of suction adherence by the suction cups is greater than or equal to the second predetermined degree of vacuum.
Accordingly, it can be determined whether the suction adhered material is a printing plate or an interleaf sheet on the basis of the detection signals of the pressure sensor. Moreover, in a case in which the pressure sensor does not output signals in accordance with respective states described above, it is determined that the suction cups are not suction-adhering any material.
As described above, an inexpensive pressure sensor can be used in order to distinguish between a photopolymer plate and an interleaf sheet taken out from a magazine. Therefore, a reduction in costs can be achieved, and there is no fear of sensitizing printing plates which have not been exposed.
Preferably, the suction adherence conveying device for printing plates of the present invention includes a suction fan which can, along with the suction cups, approach and move away from the surface of the printing plate or the interleaf sheet accommodated in the magazine, and which has a suction-adherence capacity capable of suction-adhering an interleaf sheet and incapable of suction-adhering a printing plate from a position which is spaced a predetermined distance apart from the surface of the printing plate or the interleaf sheet.
Preferably, the suction adherence conveying device of the present invention activates the suction fan at the position where the suction cups are spaced apart by a predetermined distance from the surface of the printing plate or the interleaf sheet. Thus, in a case in which the uppermost material among the materials stacked in a magazine is an interleaf sheet, the interleaf sheet can be sucked by the suction cups in a state in which only the interleaf sheet is sucked by the suction fan and the interleaf sheet and the printing plate are apart from each other.
Therefore, even in a case in which the printing plate is curled, the problem of incorrect determination at the time of sucking an interleaf sheet which is caused by the suction cups being too close to the interleaf sheet, and the problem of suction-adherence of two layers in which the photopolymer plate stacked beneath the interleaf sheet is sucked up together with the interleaf sheet are prevented, and an improvement in reliability can be achieved.
A second aspect of the present invention is a conveying device using suction adherence for separating different types of sheets of materials from one another, the conveying device comprising: (a) a magazine adapted for receiving different types of sheets of materials interleaved with another in a stack in the magazine; (b) a support structure to which the magazine removably mounts; (c) a plurality of suction cups movably mounted to the support structure, the suction cups being movable in a direction towards and away from a stack of sheet materials in the magazine; (d) a vacuum system connected through fluid communication paths to the suction cups, and a reduced pressure communicated to the suction cups through the communication paths when the vacuum system is operated and generating a suction at the suction cups, which suction adheres a sheet of material from the stack when the suction cups are moved proximate the stack; and (e) a pressure sensor in communication with the fluid communication paths, the sensor when operated, producing a signal corresponding to a degree of vacuum in the fluid communication paths for indicating whether a sheet material has adhered to the suction cups, and type of sheet material.
A third aspect of the present invention is a conveying device using suction adherence for separating different types of sheets of materials from one another, the conveying device comprising: (a) a magazine adapted for receiving different types of sheets of materials interleaved with another in a stack in the magazine; (b) a support structure to which the magazine removably mounts; (c) a suction system having a plurality of suction cups with tubes connecting the suction cups in fluid communication with one another, the suction cups being movably mounted to the support structure in a direction towards and away from a stack of sheet materials in the magazine; (d) a suction assisting section provided adjacent the suction cups, which is connected in fluid communication with the suction cups through the tubes; and (e) a pressure switch activated in response to a degree of vacuum at least equal to first and second levels, the first level indicating one type of sheet material has been suction adhered to the suction cups, and the second level indicating another type of sheet material has been suction adhered to the suction cups, the pressure switch outputting a signal when activated in accordance with the level of the degree of vacuum.
A fourth aspect of the present invention is a conveying device using suction adherence for separating different types of sheets of materials from one another, the device comprising: (a) a magazine adapted for receiving different types of sheets of materials interleaved with another in a stack in the magazine; (b) a support structure to which the magazine removably mounts; (c) a plurality of suction cups movably mounted to the support structure, the suction cups being movable in a direction towards and away from a stack of sheet materials in the magazine; (d) a vacuum pump connected through fluid communication paths to the suction cups, and a reduced pressure communicated to the suction cups through the communication paths when the vacuum pump is operated and generating a suction at the suction cups, which suction adheres a sheet of material from the stack when the suction cups are moved proximate the stack; and (e) a pressure switch activated in response to a degree of vacuum at least equal to first and second levels, the first level indicating one type of sheet material has been suction adhered to the suction cups, and the second level indicating another type of sheet material has been suction adhered to the suction cups, the pressure switch outputting a signal when activated in accordance with the level of the degree of vacuum.
A fifth aspect of the present invention is a method for distinguishing different types of sheet material from one another, the method comprising: (a) suction adhering a sheet material to suction cups, using a vacuum system to communicate a reduced pressure to the suction cups through fluid communication paths; (b) detecting the pressure in at least one of the fluid communication paths using a pressure sensor and outputting a signal from the sensor corresponding to detected pressure; and (c) determining the type of sheet material based on the signal.